Trailer Sway and un-stable

Help........Can some one help me..........I just bought a 2007 28' Salem 5th wheel by Forest Rivers .....I have a Ford F-250 short bed Super Duty 7.3 diesel engin..........A Companion hitch......When reaching speeds of 60 MPH, trailer and truck become very un-stabel.....swaying......front end feel light and hard to control........walks....hard to keep in driving lane. At times trailer goes into oscillation.
I took a long trip and was white knuckled all the way..........Allmost lost it a couple of times.
I have adjusted  the hitch up toward the cap as far as possible and had the trailer weighed and the weight distrubition seems ok.
One thing I did was mount a Generator 250 lbs on the back bumper.  When hitch to truck the fron of trailer is a little higher than the rear end of trailer..........Can not lower any more.......will hit the bed of truck..
King pin seem to be right over the rear axil. I am at lost at what the problem may be.............Help .....thinking of selling the trailer.
Thank you

Those symptoms sound like you might not have a high enough percentage of your trailer weight on the hitch pin.  Too much weight on the rear of the trailer can result in those symptoms. 

I've not towed a 5th wheel but the first thought that come to me is that you should take the generator off the rear bumper of the 5th wheel and see if that improves the handling.  You indicated the front end seems light.  I assume you mean the front end of the truck and that the steering isn't what you are used to.  Is there any way that you can move the king pin forward of the rear axle to get more weight on the front end of the pickup?  You may need a slider type hitch to do that with your short bed.  Good Luck.

Thank you so much guys for your help and input.............Both sounds like things I should try..I wonder if I remove the generator from back of trailer would this add more tongue weight ?  I can't move the king pin any  closer to the front of truck (trailer would hit cab during turns)
I also wonder if the short wheel base (being a short bed) is causing the problem ! One  clue I forgot to mention was that I got a friend to pull the trailer with his 1 ton dodge dually and it pulled straight as a string with no sway @ 76 MPH.

With a short wheelbase truck, the hitch has to be behind the rear axle or the trailer will hit the cab when turning.  This makes the setup less stable than one that has the hitch directly above or ahead of the axle.  With the hitch behind the axle, when side forces push the hitch sideways you have a lever from the hitch to the rear axle that pushes the front of the truck in the opposite direction.  Plus any weight you put behind the axle lifts weight from the front of the truck, but with that heavy diesel engine up there I can't see that being a serious problem.

If the hitch is directly above the rear axle, there is no lever action to affect the direction of the truck.  Side forces go directly through the rear axle to ground.

With the hitch ahead of the axle, side forces push both the front and rear of the truck in the same direction, a much more stable situation than pushing the front and rear in opposite directions.

You probably have a marginal setup having a short wheelbase and the hitch being behind the axle.  Having too little hitch weight on the trailer won't help, but it may not be as noticeable in a heavier truck with a longer wheelbase and the hitch being above or ahead of the rear axle.

As far as the generator goes, yes - having the generator on the back lifts weight from the hitch.  Think of the trailer as a teeter-totter, rotating around the center point of the axles.  If you add weight behind the axles, it pushes that end down and removes weight from the front.  The amount of weight removed from the hitch is the ratio of the distance of each point to the pivot in the middle of the axles.

For example, if the rear bumper is 10 ft. behind, and the hitch is 20 ft. forward of the axle centerline, the ratio is 1:2.  Putting 250 lbs. at the rear bumper will remove 1/2 of the weight, or 125 lbs, from the hitch.

Hanging a large weight at the rear of the trailer also shifts it's center of gravity rearward.  Having the center of gravity too far to the rear will also cause instability.

First thing I'd do is take the generator off of the back of the trailer and see if that helps the situation.

Two things can cause those symptoms, and the two may at first sound contradictory..
(1) Insufficient weight on the front wheels of the tow vehicle, making the front end light and hard to steer. With a5W, this is a result of improper hitch placement, i.e. on or behind the rear axle .
(2). Too little weight on the hitch (pin), resulting in a tail-heavy trailer. This can actual lifts the tow vehicle off the pavement at times and gives weird steering as well as making the trailer sway badly.

The 5W hitch should NEVER be behind the tow vehicle rear axle, or even directly over it. Must be at least a few inches in front, as Lou described. Proper placement is still possible in a short (6.5 ft) bed truck, but it is marginal.

Thank you so much Lou and Gary........Today I moved the hitch as far up as it would go.....The king pin is now 1.5" in front of the truck axle .....I took off the generator.....I tried to lower the hitch because the front of the trailer was 4" higher then the back of trailer.........Not level.........I could only come down 1" for the trailer was hitting the top of the bed. So the trailer  front now is 3" higher than the back when when hitched to the truck.  I then took it for a drive on the interstate......At speeds up to 55MPH ....No Problems Handles Great.......But if went 60 or over  I was  risking my  life and everone on the highway.........*Sigh*

The man at the Salem Factory........said I just had (a bad match) He asid I had one of the old (off the road 4x4 Ford)....and I guess I do .....But it sure is a nice truck and I have no problem pulling my Kubota Tractor on a 16' Trailer..
He also told me it was out of the question to lift the trailer up by flipping the springs ect...........Said that would only conpound the problem and make it  likely for the trailer to  turn over.

I  have a nice 28' Salem Fifth Wheel but it does not pull worth a flip.
I don't think I could get enough rent of of it in my driveway to make the payments .......
So I guess I have a 2007 Salem Fifth Wheel For Sale........Do I have any offers ?
I don't know what else to do  !          Thank you guy so much for your help and input.
Art

One other thing you might want to check is your tires.  Do you have E rated tires?  If the sidewalls are too soft, I bet that could cause some of your problem also.  I've seen too many trucks like yours pull all manner of 5th wheel without problem.  I find it hard to believe that it's just a bad pairing of truck to camper.  But I suppose it could be.  Have you thought about upgrading your truck?  While it may be nice and all, if you really want to keep the RV, it's something to think about anyway.

I'm struggling as well to believe  the truck-trailer match-u could be that bad.

Flipping the axle does indeed raise the center of gravity slightly and I suspect "dont do it" is an automatic reaction at the factory (their lawyers would insists upon it). But flipping the axle won't help your sway problem either - it just gets the trailer level.

Weights is the next question - you really need to get it weighed to see how much weight you are putting on the truck (pin).

I would also want to check the trailer axle alignment carefully. One thing you can do at home is to measure the distance from the pin to the front of the suspension on each side (or to some other point you can readily and accurately measure that is the same on each side of the suspension/axle assembly). The distance should be equal right to a small fraction of an inch. If in doubt, get an alignment shop to verify it (a truck shop can probably do this for you).

Yes, inadequate tires could be part of the problem.  But the Salem should have come with adequate tires, even if not great quality.

Can you get somebody else to pull the trailer and try it on their truck & hitch?  If you can't find a friend to help, RV dealers usually have guys on call to do deliveries and you could hire him or an hour to give it a try.

Gary.........I can't thank you enough for your time and devotion on helping me solve this problem.

Tomorrow I will check the alignment .......I already have the weights figures..........The Truck weight by itself is 7360 lbs..........The weight of the trailer hook up to truck is 8040 lbs...........The Truck hook up to trailer is 8580 lbs
I think that should be enough to determine whatever you may be thinking.
The tires on the trailer are brand new 8 Ply tires  ST225/75R15  with 65 PSI    Truck tires are 6 mo. old about 8000 miles and are 8 Ply
Front are inflated to 55 psi Rear inflated to 70 psi..per sticker on Truck.
As far as pulling the trailer with another rig.........I have done that as I stated earlier..........A friend pulled it with a dodge dually at 76mph and it pulled straight as a string with hardly any sway.

Thank You so much for your help.

Gary ..........one other thing.................Did I understand you correctly.........Are you saying that.......The fact that the trailer is 3" higher in front than the rear while being towed  Can Not  cause the swaying ?..........
If so I am a little suprized but glad because I don't think I can correct that anyway.
Seems like I read in the trailer manual that if the trailer was not level it would  cause sway.
Anyway if that is what you are saying..........That will be one less thing I need to think about !

The Truck weight by itself is 7360 lbs..........The weight of the trailer hook up to truck is 8040 lbs...........The Truck hook up to trailer is 8580 lbs

Click to expand...

Your wording is unclear to me. Which one of those weights is the truck with the trailer connected? And which is the trailer by itself? A 5W should have 17-22% of the total trailer weight resting on the truck

Sorry - I forgot you had mentioned towing it on a friend's truck. Too many different discussions going on to keep my old head straight!  ??? And the trailer axle alignment must be ok if it tows on the friend's  truck without problems. If nothing else was changed when towing on the other truck, that means the problem is your truck and that usually means hitch position or maybe the weight carrying capacity of the truck. Too much weight on the rear of the truck actually lifts enough weight off the front wheels to get the sudden, squirrel-ly handling you describe. Moving the hitch forward helps that, but you tried that already (though a mere 1.5" in front of the axle is still marginal at best). The nose-up attitude contributes to the handling problem, but in and of itself should not have the effect you are experiencing.

I'm at loss to make further suggestions without actually seeing the truck, measuring various things and such. There is no reason a truck like yours should not pull that trailer nicely.  I once owned a F250 7.3L diesel myself and towed a 11,000 lb trailer. It was along bed, though, and that allowed a good hitch position, several inches forward of the axle. I'm thinking yours must be a short bed, short wheel base model, but there still should be room.

The fact that the trailer is 3" higher in front than the rear while being towed  Can Not  cause the swaying ?....

Click to expand...

I've learned never to say "cannot" with respect to an RV,  but in general a modest nose-up attitude should not cause sway. Certainly nothing like what we are discussing here. The major concern with a nose-up attitude is that, when braking suddenly, the pin/hitch tends to lift the rear of the truck and dive the front end at the critical moment and can make it react strangely. However, it also tends to transfer trailer weight off the hitch and back onto the trailer axles, and if enough weight comes off the pin it can indeed increase the tendency to sway. I would not expect 3" to do the latter, but it doesn't help either.

Gary............Sorry about me not making the weights clear enough.................According to my calculations........my hitch weight would be 13.1%..........and that was weighed with the generaton on back of trailer..............This is low of your figures        17%to 22 % and by the way the rig feels I suspect that if I had more hitch weight it might be more stable at hight speed.

Now the question becomes................What is the best way to add hitch weight ?
Thank you so much for your help

13% IS low for a 5w - 20% or more is typical. But more hitch (pin) weight also makes the weight distribution on the truck more critical.  I was hoping you would have axle weights rather than gross weight for the truck. Presumably the pin weight was near the same when your friend towed it. As discussed elsewhere, the nose-up attitude probably shifted a bit of weight to the trailer axles, so maybe the friend had a small advantage there IF it was level on his truck.

You could try placing some sandbags or whatever in the truck bed as far forward as possible and see if it helps. An extra 250-300 lbs in the front of the bed should help keep the truck front end down and give you an idea whether weight distribution is the problem. Even if you just see a +5 mph difference in when the sway starts, you would know you are on the right track. If that is it, the moving the hitch would be the answer, I think

Let me try to explain how I calculated this.


Truck with trailer attatched = 8580
Trailerweighed while being hook up to truck = 8040
So both trailer and truck together =16620
Truck alone =7360

So 16620-7360=9260  .....so trailer weight is 9260
Truck weight while trailer attatch is 8580
So 8580-7360=1220 which is the hitch weight

1220 is 13.1% of the total trailer weight


This may not be right ......But this is the way I calculated it !

Do you have room for your generator in the very front of your truck bed with the trailer attached?  That's an easy way to get 250 lbs. off of the back bumper and transferred to the truck.

Will Hello Gary and Lou.............Bet you thought you had heard the last from me..........I don't know how much you guy are making ..But you are NOT being paid enough !
Today I took the trailer for a spin on the Interstate with 300 lbs of sand just ahead of the hitch on truck.........It difinately was alot better .....I had more control of steering and notice when side forces happened the truck and trailer went the same direction ..Not opposite which is GOOD ! I don't feel like I am completely out of the woods yet and am wondering how I can still add more hitch weight on a permanent basic.
Would putting sand bags in the cargo compartment in the front of the trailer accomplish this? I feel like another 300 lbs would help alot.
Gary you mention that moving the hitch would be the solution and that might would work..........but I cannot move it any farther foward it is already adjusted as far foward as it will go.
I really appreciate you guys for getting me going in the right direction.........I really mean it.......You are not being Paid enough......Tell your Boss to call me !

Later

Art

You have demonstrated that the problem is one of weight distribution, though I do not see why the same problem did not exhibit when towed by the friends truck. That's why I suspected hitch location, assuming his is better located than yours. You may need to physically move the mounts for the hitch - it may not have been placed for enough forward. That will place more weight on the front wheels of the truck, which helps the stability of the truck itself.

I'd love to see axle-by-axle weights on the truck, with and without the trailer attached. I'm still not sure if the problem is trailer balance or simply because the hitch weight is putting the truck off balance, i.e. actually lifting weight off the front wheels when the trailer weight pushes down on the back.

In any case, 13.1% is a low hitch weight for a fifth wheel. I would consider 15% an absolute minimum and the norm is closer to 20%. So yes, you need weight forward and yes, you can add it to the front on the trailer. But if the problem is how the weight bears down on the truck, then more weight in the trailer king pin (hitch) might actually make it worse. With a lot of weight on or slightly behind the truck rear axle, the truck acts like a teeter-totter and the weight pushes the rear end down and lifts the front end up, which quickly results in really scary steering.

Have you tried pulling the trailer without the 250# generator on the bumper?

Also, this may be a dumb idea, but can you move the generator to the bed of the truck between the hitch and the back window of the truck? If it will go there without interfering with the movement of the 5th wheel, that would add weight to the hitch pin area.  I had to do that often when I pulled a gooseneck (similar to a 5th wheel) horse trailer,  My bales of hay could be placed strategically  in the bed of the truck.

Marsha~